In a hydrostatic or hydrodynamic plain bearing, in which the actual support is carried out by a formed thin lubricating film consisting of a fluid (e.g. of an oil), a measurement of the temperature of the lubricant in the lubricating film or a temperature measurement in the adjacent sliding surfaces provides information about the state of the bearing and is therefore especially suitable for monitoring the operation.
Thus it is known from EP 0 161 644, in a plain bearing for the early detection of damage, to monitor the temperature in the region of the sliding layer in order to be able to take countermeasures in good time in the event of a noticeable increase in temperature. In this case, however, a change in the lubricant temperature is recorded with a considerable time delay and only indirectly. Even if the temperature sensor were to be run directly to the surface or sliding surface, the temperature of the bearing segment at best would be measured. The lubricant or fluid temperature may locally be markedly above this, since 90-97% of the heat generated in the fluid is dissipated by the fluid itself, that is to say past the temperature sensor; only 5% of the heat in terms of the order of magnitude is directed through the bearing segment.
A direct measurement of the lubricant temperature in the lubricating film is not known in the prior art. The problem with the direct measurement is that the film, for example in the case of oil as lubricant, is only 20 μm to about 200 μm thick, so that no probes can be fitted. German Patent 883 984 specifies a bearing design for rolling mills which is supplied with an excess lubricant quantity for cooling, which is larger than the lubricant quantity which is to penetrate into the lubricating gaps. The excess quantity is drawn off from fresh-oil chambers through a return line. German Patent 883 984 proposes to arrange a temperature sensor in this return line in order to determine the temperature of the bearing surface. In this case, however, there is on the one hand the risk of the measurement being distorted by feed lubricant; on the other hand, the proposed measuring method can only be used in special bearings which are operated with excess oil. Furthermore, there are considerable uncertainties when drawing conclusions about the temperature in the bearing gap, since of course the measured medium does not originate explicitly from the bearing gap.